Most times when I start writing a post, I start off saying ‘this type of jewellery or this stone has been used in jewellery for thousands of years’. Well, this post is no different, it’s about gold and gold has been used for jewellery for a very long time. Gold is a heavy metal, very malleable, able to turned into thin threads, and resistant to most corrosive elements. It doesn’t tarnish like silver and it doesn’t cause skin irritation. It is a soft metal and needs to mixed with other metals like silver or copper so it can be worked for jewellery or coins.
Gold is usually a yellow colour but its colour can be changed when other metals are mixed with it. Adding copper and removing silver results in a pink shade of gold, rose gold. Green gold, which is not seen in modern jewellery, is created by adding silver, zinc or cadmium as the additive, and white gold is created by adding metals like zinc, nickel and silver.
The quality of gold is measured in carats. Pure gold is 24 carats (ct) or karats (kt) if American), but is very soft and so others metals are added. The highest quality gold used for jewellery is 22 ct. The number of the carat tells us what percentage of other metals has been added to the gold. The higher the number, the less alloy has been added. For example, if we take 9ct gold, this means that 37.5% (9/24) of the metal is gold, the rest alloys, while 18ct gold (18/24) means that 75% is gold. So, you may see that some 9ct items will be marked .375 and 18ct ones are marked .750.
Countries set their own standards for gold. While the minimum carat for gold is usually 9ct (in Australia, the UK, Portugal, Austria and Canada), in the USA, the minimum carat is now 10ct, while in Greece and Denmark, for example, the minimum carat is 8ct. In France, 18ct is the minimum standard unless the item is intended for export.
Antique jewellery is most commonly made out of 18ct, 15ct, and 9ct but you will also see 14ct, 12ct and 10ct.
Next post, I will talk about hallmarking.